I've been using 6mm black tape on the upper edge of my TRB5 fretless (for some reason Yamaha side-dotted it as though it was fretted...), but it never occurred to me to cover the whole board. Kudos!
It might be interesting to mix cobalt flatwound E string with steel flats for other strings. That would brighten the E only, and you'd still have the same tactile experience.
Blimey - a Fender I actually like the looks of! Sadly, I don't need it and there are too many other things already on the GAS list...
Good luck with your sale!